1. Technical Field
Embodiments of the present disclosure relate generally to loop filters, and more specifically to loop filter for current-controlled-oscillator-based phase locked loop (PLL).
2. Related Art
Current-controlled oscillators are often used in phase-locked loops (PLL). The output frequency of a current-controlled oscillator is determined by the magnitude of a current provided as input to the current-controlled oscillator. For example, when a current-controlled oscillator is implemented as a gated-ring oscillator (GRO), the magnitude of the power-supply current to the inverters in the GRO can be used to set a desired output frequency of the GRO.
A loop filter of a PLL is used to perform low-pass filtering operation of the output of a phase detector used in the PLL. The low-pass filtered output of the loop filter is provided as input to control the frequency generated by the current-controlled oscillator. The design of the loop filter generally needs to support requirements such as small implementation area, low noise contribution, etc.